An absolute position measuring encoder having an ABS/INC integrated pattern obtained by integrating an absolute pattern and an incremental pattern together has been suggested in the second and fourth embodiments of Japanese Patent Application Laid-Open No. 2009-2702 (hereinafter, referred to as Patent Literature 1). This ABS/INC integrated pattern allows a single pattern to have two types of information about an absolute pattern and an incremental pattern, thereby making it possible to narrow a scale width thereof.
However, since the ABS/INC integrated pattern has two types of information about an absolute pattern signal and an incremental pattern signal, a complicated analysis is required in order to separate these two types of information from each other. Thus, there is a problem that a high-performance processing circuit is required or a long operation time is needed. In Patent Literature 1, for example, as shown in FIG. 1 corresponding to FIG. 8 of Patent Literature 1, an absolute pattern signal (FIG. 1C) is separated off from a received light signal (FIG. 8B) by means of a low-pass filter. However, the employment of the low-pass filter leads to a longer signal processing time, thereby being unable to perform high-speed processing.